Vehicle emissions have long been identified as a major contributor to air pollution. As such, in geographical areas having particularly poor air quality, the United States federal government, through the Environmental Protection agency (xe2x80x9cEPAxe2x80x9d), has mandated vehicle emission inspection and maintenance programs. The intent or objective of these vehicle emission inspection and maintenance programs is to identify vehicles which are no longer performing acceptably, i.e., vehicles which are releasing more polluting emissions than is acceptable. Vehicles identified as not performing acceptably must then be appropriately repaired.
In implementing vehicle emission inspection and maintenance programs, various apparatus, methods, and testing protocols have been developed and are being used across the United States. In this regard, the local municipality or similar governing body normally makes the decision as to which apparatus, method, and/or protocol to employ. For example, some municipalities have opted for centralized testing locations, others have opted for decentralized testing locations, and still others have opted for a hybrid centralized/decentralized systems. In most cases, the ultimate decision as to which apparatus, method, and/or protocol to employ depends on a combination of factors, including, for example: practicality, costs, and input from interested third parties. Thus, there are often wide variations between the apparatus, methods, and/or protocols employed in different geographic areas. Such variations often result in differences in the reliability and accuracy of the testing, along with differences in the amount of labor and skill required to conduct the testing and to maintain the equipment associated with that testing.
A few of the simpler vehicle emission test methods are: (1) the Idle Mode Test, which measures emissions from an idling vehicle; and (2) the Loaded Mode Test, which measures emissions from vehicles driven at a constant speed. Although these two tests provide general baseline information regarding vehicle emissions, they are not representative of xe2x80x9creal worldxe2x80x9d driving. As a result, both the Idle Mode Test and the Loaded Mode Test often tend to produce false positives. In other words, a vehicle might pass the Idle Mode Test or Loaded Mode Test even though that vehicle is not in compliance with federal guidelines. Quite clearly, such testing failures are potentially detrimental to the air quality of a geographic area because vehicles which require repair are not appropriately identified, thus allowing for excessive release of polluting emissions.
To address these problems, more rigorous test methods and protocols have been developed, including the Acceleration Simulation Mode (ASM) concentration test and Transient Mass Emission Inspections (TMEI). Such test methods are clearly preferred as compared to the Idle Mode Test and the Loaded Mode Test; however, along with improved performance comes increased costs.
First, the ASM concentration test can be used in both centralized and decentralized testing programs. In an ASM concentration test, vehicles are driven at a fixed speed under a heavy load. Nevertheless, because the vehicles are artificially loaded, false failures can result. In other words, a vehicle might fail the ASM concentration test even though that vehicle is in compliance with federal guidelines. Although false failures are not detrimental to the air quality of a geographic area, a false failure can be costly to the vehicle owner who must have the vehicle examined at a repair or maintenance facility, and then must have the vehicle re-tested. Furthermore, a high percentage of false failures tends to result in public distrust of vehicle emission testing.
Among the most advanced and accurate test methods are Transient Mass Emission Inspections (TMEI), such as the IM240 and IM147. In TMEI, a vehicle is tested at a variety of velocities, accelerations, and decelerations. These velocities, accelerations, and decelerations (collectively referred to as a xe2x80x9cdrive tracexe2x80x9d) are representative of xe2x80x9creal worldxe2x80x9d driving conditions and engine loads. For example, an IM240 test includes a series of accelerations, decelerations and speeds ranging from zero miles per hour (MPH) to fifty-six MPH over a 240-second testing period. For the duration of the testing period, emissions, including hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO2), and the oxides of nitrogen (NOx), are individually accumulated over the drive trace and normalized for the distance traveled. This recorded mass per distance, normally reported as grams per mile (GPM), is then reported as the vehicle""s test score. The vehicle""s test score for each accumulated pollutant is compared to a federally defined standard for that vehicle and that particular pollutant. A score exceeding the defined standard is considered a failure.
Thus, since pollutant mass is measured in TMEI, as opposed to pollutant concentration (Idle Mode, Loaded Mode and ASM testing), a more accurate determination of the vehicle emission characteristics can be generated. Nevertheless, TMEI have some shortcomings. Conventional TMEI do not lend themselves well to decentralized testing. Furthermore, they are inherently complex and costly to implement, operate, and maintain.
It is therefore a paramount object of the present invention to provide a method and system for vehicle emission testing that relies on transient test drive traces with xe2x80x9creal worldxe2x80x9d velocities, accelerations, decelerations, and loading, a method and system that provides a measurement of pollutant mass rather than pollutant concentration, yet has relatively low implementation, operating, and maintenance costs.
This and other objects and advantages of the present invention will become apparent upon a reading of the following description.
This present invention pertains to a method and system for vehicle emission testing. The method and system of the present invention relies on transient test drive traces with xe2x80x9creal worldxe2x80x9d velocities, accelerations, decelerations and loading. More importantly, however, although the method and system of the present invention measures pollutant concentration, it provides for conversion of the measured pollutant concentration into its corresponding pollutant mass, thereby allowing for the calculation of a vehicle""s emission test scores for one or more common pollutants in units of mass per distance. Through the use of the method and system of the present invention, significantly more accurate results can be obtained as compared to prior art test methods, and without the implementation, operating, and maintenance costs of comparable test methods.